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Gravel hardness effect on compaction characteristics of gravelly soil

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Journal of Mountain Science 2024年第4期21卷 1432-1443页

作者： SHI Yunfang LI Shengang JIANG Chen LIU Jinning school of resources and civil engineering Northeastern UniversityShenyang 110004China

The compaction characteristics of gravelly soil are affected by gravel hardness.To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,heavy compaction tests and crushing tests were conducted on gravelly soils with gravels originated from hard,soft and extremely soft rocks.According to orthogonal experiments and variance analysis,it was found that hardness has a significant impact on the maximum dry density of gravelly soil,followed by gravel content,and lastly,moisture content.For gravel compositions with an average saturated uniaxial compressive strength less than 60 MPa,the order of compacted maximum dry density is soft gravels>hard gravels>extremely soft gravels.Each type of gravelly soil has a threshold for gravel content,with 60%for hard and soft gravels and 50%for extremely soft gravels.Beyond these thresholds,the compacted dry density decreases significantly.There is a certain interaction between hardness,gravel content,and moisture content.Higher hardness increases the influence of gravel content,whereas lower hardness increases the influence of moisture content.Gravelly soils with the coarse aggregate(CA)between 0.7 and 0.8 typically achieve higher dry densities after compaction.In addition,the prediction equations for the particle breakage rate and CA ratio in the Bailey method were proposed to estimate the compaction performance of gravelly soil preliminarily.The results further revealed the compaction mechanism of different gravelly soils and can provide reference for subgrade filling construction.

关键词： Gravelly soil Hardness Compaction characteristics Crushing characteristics Particle breakage rate Bailey method

Mechanical properties and fracture surface roughness of thermally damaged granite under dynamic splitting

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Deep Underground Science and engineering 2024年第1期3卷 103-116页

作者： Yijin Qian Peng Jia Songze Mao Jialiang Lu school of resources and civil engineering Northeastern UniversityShenyangChina

In order to understand the mechanical properties and the fracture surface roughness characteristics of thermally damaged granite under dynamic splitting,dynamic Brazilian splitting tests were conducted on granite samples after thermal treatment at 25,200,400,and 600℃.Results show that the dynamic peak splitting strength of thermally damaged granite samples increases with increasing strain rate,showing obvious strain‐rate sensitivity.With increasing temperature,thermally induced cracks in granite transform from intergranular cracks to intragranular cracks,and to a transgranular crack network.Thermally induced damages reduce the dynamic peak splitting strength and the maximum absorbed energy while increasing the peak radial strain.The fracture mode of the thermally damaged granite under dynamic loads is mode Ⅱ splitting failure.By using the axial roughness index Z2 a,the distribution ranges of the wedge‐shaped failure zones and the tensile failure zones in the fracture surfaces under dynamic Brazilian splitting can be effectively identified.The radial roughness index Z_(2)^(r)is sensitive to the strain rate and temperature.It shows a linear correlation with the peak splitting strength and the maximum absorbed energy and a linear negative correlation with the peak radial strain.Z_(2)^(r)can be used to quantitatively estimate the dynamic parameters based on the models proposed.

关键词： dynamic splitting fracture surface roughness granite strain rate thermal treatment

Precise regulation of the phase transformation for pyrolusite during the reduction roasting process

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 81-90页

作者： Ruofeng Wang Peng Gao Shuai Yuan Yanjun Li Yingzhi Liu Cheng Huang school of resources and civil engineering Northeastern UniversityShenyang 110819China National-Local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang 110819China

The mechanism involved in the phase transformation process of pyrolusite (MnO_(2)) during roasting in a reducing atmosphere was systematically elucidated in this study,with the aim of effectively using low-grade complex manganese ore resources.According to single-factor experiment results,the roasted product with a divalent manganese (Mn^(2+)) distribution rate of 95.30% was obtained at a roasting time of 25 min,a roasting temperature of 700℃,a CO concentration of 20at%,and a total gas volume of 500 mL·min^(-1),in which the manganese was mainly in the form of manganosite (MnO).Scanning electron microscopy and Brunauer–Emmett–Teller theory demonstrated the microstructural evolution of the roasted product and the gradual reduction in the pyrolusite ore from the surface to the core Thermodynamic calculations,X-ray photoelectron spectroscopy,and X-ray diffractometry analyses determined that the phase transformation of pyrolusite followed the order of MnO_(2)→Mn_(2)O_(3)→Mn_(3)O_(4)→MnO phase by phase,and the reduction of manganese oxides in each valence state proceeded simultaneously.

关键词： pyrolusite phase transformation reduction roasting microstructural evolution reaction mechanism

Recent process developments in beneficiation and metallurgy of rare earths:A review

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Journal of Rare Earths 2024年第4期42卷 629-642页

作者： Shaokai Cheng Wenbo Li Yuexin Han Yongsheng Sun Peng Gao Xiaolong Zhang school of resources and civil engineering Northeastern UniversityShenyang110819China National-local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang110819China

Rare earth elements(REEs)are irreplaceable materials supporting low-carbon technology and equip-ment,and their commercial demand and strategic position are becoming increasingly prominent.With the continuous depletion of rare earth(RE)resources,developing high-efficiency beneficiation and eco-friendly metallurgical processes has attracted widespread attention.This paper reviews the major minerals exploited for RE production and their deposits,as well as the beneficiation and metallurgical processes of RE minerals.Bastnaesite,monazite,mixed RE ores,and ion-adsorption clays are the main raw materials in the world to date.RE-bearing ores(except ion-adsorption minerals)are generally beneficiated by flotation,gravity and magnetic separation techniques.The mainstream metallurgical processes for bastnaesite,monazite and mixed RE concentrates are oxidation roasting-HCl leaching,caustic soda decomposition and high-temperature concentrated sulfuric acid roasting,respectively.Ion-adsorption clays are directly processed by in situ leaching-precipitation/solvent extraction.To achieve the sustainable development of RE resources,it is essential to further explore innovative techniques to achievecomprehensive utilization and cleaner production.

关键词： Rare earths Beneficiation processes Metallurgical processes Cleaner production

Energy evolution and structural health monitoring of coal under different failure modes:An experimental study

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 917-928页

作者： Yarong Xue Xueqiu He Dazhao Song Zhenlei Li Majid Khan Taoping Zhong Fei Yang School of Civil and Resources Engineering University of Science and Technology BeijingBeijing 100083China Zhong-an Academy of Safety engineering Beijing 100083China

Structural instability in underground engineering,especially in coal-rock structures,poses significant safety risks.Thus,the development of an accurate monitoring method for the health of coal-rock bodies is crucial.The focus of this work is on understanding energy evolution patterns in coal-rock bodies under complex conditions by using shear,splitting,and uniaxial compression tests.We examine the changes in energy parameters during various loading stages and the effects of various failure modes,resulting in an innovative energy dissipation-based health evaluation technique for coal.Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading,indicated by fluctuations in elastic energy and dissipation energy density.For tensile failure,the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress.On the other hand,shear failure is described by “high accumulation and low dissipation” in energy trends.Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization,and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples.A novel mathematical and statistical approach is developed,establishing a dissipation energy anomaly index,W,which categorizes the structural health of coal into different danger levels.This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments,contributing to the development of structural health monitoring technology.

关键词： energy dissipation structural health monitoring early warning coal-rock mechanics failure mode

Literature overview of basic characteristics and flotation laws of flocs

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 943-958页

作者： Wanzhong Yin Yu Xie Zhanglei Zhu school of resources and civil engineering Northeastern UniversityShenyang 110819China College of Chemistry and Chemical engineering Xi’an University of Science and TechnologyXi’an 710054China

Flocculation flotation is the most efficient method for recovering fine-grained minerals,and its essence lies in flotation and recovery of flocs.Fundamental physical characteristics of flocs are mainly determined by their apparent particle size and structure(density and morphology).Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water treatment.However,the influence of floc characteristics on flotation has not been widely studied.Based on the floc formation and flocculation flotation,this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure,summarizing the interaction between floc particle size and structure.Moreover,it thoroughly discusses the effect of floc particle size and structure on floc floatability,further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and bubbles.Thus,it is observed that floc particle size is not the only factor influencing flocculation flotation.Within the appropriate apparent particle size range,flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation,thereby resulting in enhanced flotation performance.This study aims to provide a reference for flocculation flotation,targeting the development of more efficient and refined flocculation flotation processes in the future.

关键词： flocs basic characteristics particle size and structure flotation laws bubbles

2.5-dimension soil seismic response to oblique incident waves based on exact free-field solution

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Frontiers of Structural and civil engineering 2024年第2期18卷 216-235页

作者： Yeongbin Yang Zeyang Zhou Xiaoli Wang Xiongfei Zhang Zhilu Wang school of civil engineering Chongqing UniversityChongqing 400045China school of civil engineering and Architecture Chongqing University of Science and TechnologyChongqing 401331China

With the three dimensional(3D)oblique incident waves exactly determined for the free field,the soil seismic responses in both frequency and time domains are studied by the 2.5 dimension(2.5D)finite/infinite element method.First,the free-field responses in frequency domain are solved exactly for 3D arbitrary incident P and SV waves,which requires no coordinate conversion or extra effort for SV waves with super-critical incident angles.Next,the earthquake spectra are incorporated by the concept of equivalent seismic forces on the near-field boundary,based only on the displacements input derived for unit ground accelerations of each frequency using the 2.5D approach.For the asymmetric 2.5D finite/infinite element model adopted,the procedure for soil seismic analysis is presented.The solutions computed by the proposed method are verified against those of Wolf’s and de Barros and Luco’s and for inversely calculated ground motions.Of interest is that abrupt variation in soil response occurs around the critical angle on the wave propagation plane for SV waves.In addition,the horizontal displacements attenuate with increasing horizontal incident angle,while the longitudinal ones increase inversely for 3D incident P and SV waves.

关键词： 3D oblique incident wave seismic response analysis 2.5D approach infinite element half-space

Stability of water yield in watersheds

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Science China Earth Sciences 2024年第2期67卷 483-496页

作者： Yu YAN Zhiyong LIU Xiaohong CHEN Liyan HUANG Center for Water resources and Environment School of Civil EngineeringSun Yat-Sen UniversityGuangzhou510275China Southern Marine Science and engineering Guangdong Laboratory(Zhuhai) Zhuhai519082China

The hydrological system of a watershed is intricately influenced by both underlying characteristics and climate conditions.Understanding the variability in water yield is essential for effective water resources management and water security in the context of changing environments.In this study,we adopted the Budyko framework and leveraged simulations from the CMIP6 model to investigate the compensation effects of climate and underlying characteristics on watershed water yield.Based on Taylor expansion and Budyko framework,we estimated the sensitivity of watershed water yield to climate and underlying characteristics(the first-and second-order partial derivatives).By combining external watershed characteristics(e.g.,water yield ratios and underlying characteristics)with internal sensitivity coefficients,this study further used vine copula and principal component analysis to quantify the stability of watershed water yield.Our findings show:(1)Water-yield changes related to underlying characteristics could be offset by climate-related water-yield changes across all climate zones,maintaining the water yield ratio steady(i.e.,the compensation effects).(2)However,global watersheds will turn more sensitive to underlying characteristics and less sensitive to climate variation in the future.Both climate-and underlying-related sensitivities increase in watersheds with arid climates.(3)The stability of watershed water yield will gradually diminish in the future.From 1901–1950to 2051–2100,the global stability of 280 watersheds drops from 0.054 to 0.021(i.e.,stability index identified by the joint probability).Particularly,the largest change in stability of water yield reaches-0.347±0.18 in arid regions.In semi-arid,semihumid,and humid regions,the changes are-0.039±0.010,-0.028±0.005,and-0.005±0.002,respectively.The findings provide a reference for the future sustainable water resources development under climate change,highlighting the vulnerability of the water resources in arid and semi-arid watersheds.

关键词： Hydrological system stability Compensation effects on water yield Sensitivities Budyko-Fu decomposition framework Global watersheds

Heterogeneous information phase space reconstruction and stability prediction of filling body–surrounding rock combination

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1500-1511页

作者： Dapeng Chen Shenghua Yin Weiguo Long Rongfu Yan Yufei Zhang Zepeng Yan Leiming Wang Wei Chen School of Civil and Resources Engineering University of Science and Technology of BeijingBeijing 100083China Production Technology Department Longshou MineJinchuan Group Co.Ltd.Jinchang 737100China school of civil engineering and Architecture East China Jiaotong UniversityNanchang 330013China

Traditional research believes that the filling body can effectively control stress concentration while ignoring the problems of unknown stability and the complex and changeable stress distribution of the filling body–surrounding rock combination under high-stress conditions.Current monitoring data processing methods cannot fully consider the complexity of monitoring objects,the diversity of monitoring methods,and the dynamics of monitoring data.To solve this problem,this paper proposes a phase space reconstruction and stability prediction method to process heterogeneous information of backfill–surrounding rock combinations.The three-dimensional monitoring system of a large-area filling body–surrounding rock combination in Longshou Mine was constructed by using drilling stress,multipoint displacement meter,and inclinometer.Varied information,such as the stress and displacement of the filling body–surrounding rock combination,was continuously obtained.Combined with the average mutual information method and the false nearest neighbor point method,the phase space of the heterogeneous information of the filling body–surrounding rock combination was then constructed.In this paper,the distance between the phase point and its nearest point was used as the index evaluation distance to evaluate the stability of the filling body–surrounding rock combination.The evaluated distances(ED)revealed a high sensitivity to the stability of the filling body–surrounding rock combination.The new method was then applied to calculate the time series of historically ED for 12 measuring points located at Longshou Mine.The moments of mutation in these time series were at least 3 months ahead of the roadway return dates.In the ED prediction experiments,the autoregressive integrated moving average model showed a higher prediction accuracy than the deep learning models(long short-term memory and Transformer).Furthermore,the root-mean-square error distribution of the prediction results peaked at 0.26,thus outperforming the no-prediction method

关键词： deep mining filling body–surrounding rock combination phase space reconstruction multiple time series stability prediction